Methods and devices based on immunodiffusion are known from for example U.S. Pat. No. 4,757,002, U.S. Pat. No. 3,990,852 and U.S. Pat. No. 4,562,147. Immunochromatographic methods based on lateral flow are known from EP 0 291 194, EP 0 284 232, EP 0 250 137, and WO 86/03839. A diagnostic device comprising a post-filter unit is known from U.S. application 2003/0049857.
U.S. Pat. No. 4,562,147 provides a radial immunodiffusion enzyme assay method for testing of pseudorabies antibodies in swine and other animals. Agar test plates are provided including an underlying adherent coating of solubilized non-infectious swine pseudorabies antigen. The result of the test is obtained from the diameters of the resulting colored zones which correlate with the titers obtained by the official virus neutralization test.
EP 0 291 194 relates to assays involving specific binding, especially immunoassays and devices therefore. The analytical test device comprises a hollow casing, containing a dry porous carrier, which communicates indirectly with the exterior of the casing via a bibulous sample receiving member. The carrier contains in a first zone a labeled specific binding reagent and in a second zone spatially distinct from the first zone an unlabelled specific binding reagent for the same analyte. When the test is performed the sample solution is contacted with the test device directly which increases the risk of overflow to the second zone.
EP 0 284 232 provides a solid phase assay for determining the presence or absence of analyte in a liquid sample. A test strip of the invention has a tracer movably supported on a first portion and a binder immobilized on a second portion. A disadvantage of this method is that the sample solution is contacted with the test during the performance of the test, which increases the risk of overflow to the second portion.
EP 0 250 137 describes an immunoassay using colloidal gold for detecting a ligand in a sample, where a membrane strip is contacted with a sample and simultaneously or successively with a liquid reagent containing a ligand binding partner or ligand labeled with colloidal gold. A disadvantage of this method is that an additional liquid reagent containing the labeled ligand is needed.
WO 86/03839 illustrates a solid phase diffusion assay where the sample is first mixed with a labeled binding substance and then applied to a region of a support with immobilized adsorbent molecules and allowed to diffuse therein. The diffusion pattern is visualized and measured.
US 2003/0049857 relates to a diagnostic device comprising a test unit and a post-filter unit. The post-filter unit comprises a label zone containing a dried indicator reagent. The indicator reagent is drawn trough the post filter unit with a separate buffer and the sample is added directly to the test unit comprising the reaction zone. This however makes the test awkward to use.
It is evident from the description of the background art that a multitude of different test kits are available. A wide variety of test kits are available commercially and many of them are intended for home use. In spite of their convenient formats, there are many risks for errors if they are used in an erroneous manner. This risk is imminent when the test device is used for sampling, which may be both impractical and inconvenient. Especially, when the test device is used as a sampling device or for collecting the sample there is a risk that the sensitive reagents and the structure of the analytical device is destroyed or disturbed. Further solid samples or liquid samples which need to be diluted require an additional step.
The present invention provides an improved detection system for immunochemical tests involving a filter device which enables a liquid sample with or without dilution or a diluted solid sample to be filtered through the device and the sample solution together with the labeled specific binding reagent to be transferred and mobilized from the filter material in a controlled manner. Due to the two-part system the analyzer device is not in direct contact with the liquid sample solution, thereby minimizing the possibilities that the reagents in and the structure of the analyzer device are destroyed or disturbed by the sampling procedure. The device of the present invention is especially advantageous for tests where the sample need to be diluted.
It should be noted that all documents cited in this text (“herein cited documents”) as well as each document or reference cited in each of the herein-cited documents, and all manufacturer's literature, specifications, instructions, product data sheets, material data sheets, and the like, as to the products mentioned in this text, are hereby expressly incorporated herein by reference.